My friend asked me this question the other day , and although it sounds simple and foolish i was unable to find an answer to it even after hours of internet research . my friend said that us humans can feel joy and euphoria and that's actually what drives most of us in life . now less intelligent creatures like dogs , cats and so on .. can also feel "joy" . now he asked what's the simplest architecture or physical manifestation that can "Feel" or be at a state of "joy" . and can an entity not be intelligent at all but feel joy ? he also said that imagine there was an isolated brain , that is at a continuous state of extreme euphoria , without being able to interact with the external world or anything , it's just an entity having fun ... how simple can that entity get ? thank you .